Adding BT_LE_ADV_OPT_CODED causes periodic advertising to stop running.

[joey]

HI

I am currently using nRF54L15 with NCS 3.0.0 SDK, running the periodic_adv_conn example. I made the following modifications to the extended advertising and periodic advertising:

------------------------------------------------------------------
struct bt_le_adv_param param = {
    .id = BT_ID_DEFAULT,    
    .sid = 0,               
    .secondary_max_skip = 0,
    .peer = NULL,           
    .interval_min = BT_GAP_ADV_SLOW_INT_MIN,
    .interval_max = BT_GAP_ADV_SLOW_INT_MAX,
    .options = BT_LE_ADV_OPT_EXT_ADV | BT_LE_ADV_OPT_CODED | BT_LE_ADV_OPT_USE_IDENTITY
};

err = bt_le_ext_adv_create(&param, &adv_cb, &pawr_adv);
if (err) {
    printk("Failed to create advertising set (err %d)\n", err);
    return;
}

---------------------------------------------------------------------

#define NUM_RSP_SLOTS      10
#define NUM_SUBEVENTS      5
#define PACKET_SIZE        5
#define SUBEVENT_INTERVAL  0xAC

static const struct bt_le_per_adv_param per_adv_params = {
    .interval_min = 0x5280,                 
    .interval_max = 0x5280,
    .options = 0,
    .num_subevents = NUM_SUBEVENTS,
    .subevent_interval = SUBEVENT_INTERVAL,  
    .response_slot_delay = 0x5,              
    .response_slot_spacing = 0xA0,          
    .num_response_slots = NUM_RSP_SLOTS,   
};

CONFIG_BT=y

CONFIG_BT_BROADCASTER=y

CONFIG_BT_EXT_ADV=y

CONFIG_BT_PER_ADV=y

CONFIG_BT_DEVICE_NAME="xxxx"

CONFIG_BT_PER_ADV_SYNC_TRANSFER_SENDER=y

CONFIG_BT_PER_ADV_RSP=y

CONFIG_BT_MAX_CONN=1

CONFIG_BT_CENTRAL=y

CONFIG_BT_PRIVACY=y

CONFIG_BT_SMP=y

CONFIG_LOG=y

CONFIG_SERIAL=y

CONFIG_UART_ASYNC_API=y

CONFIG_FLASH=y

CONFIG_FLASH_JESD216_API=y

CONFIG_EVENTS=y

CONFIG_BT_CTLR_ADV_DATA_LEN_MAX=255

CONFIG_BT_CTLR_SDC_PERIODIC_ADV_RSP_TX_MAX_DATA_SIZE=249

CONFIG_BT_CTLR_PHY_CODED=y

CONFIG_BT_CTLR_ADV_EXT=y

# CONFIG_BT_USER_PHY_UPDATE=y

CONFIG_BT_EXT_ADV_CODING_SELECTION=y

After making these changes, I found that when starting to run, the periodic advertising operates normally. However, once the extended advertising begins, the periodic advertising stops running, and only the extended advertising continues to operate normally. Why is this happening?

Thanks

[joey]

I misunderstood the issue. The periodic synchronized advertising is actually running without problems, but the interval time is set relatively long.

When using BT_LE_ADV_OPT_CODED, what is the maximum number of bytes supported for periodic synchronized advertising? After I set PACKET_SIZE to 140, bt_le_per_adv_set_subevent_data returned an error with status code 0x45 from bt_hci_core (opcode 0x2082), indicating the data bytes are too long.

[Vidar Berg]

I expect you should be able to send longer packets if you extend the interval, or have you tried that already? Coded phy requires roughly 8x the time on air to transmit the same payload compared to the 1m phy.

You have already looked this up in the specification but I'm just including this excerpt for reference anyway:

"The Subevent_Data arrayed parameter contains the advertising data to be transmitted in the subevent of the advertising set. If the combined data length is greater than the maximum that the Controller can transmit within the current subevent interval, then all data shall be discarded and the Controller shall return the error code Packet Too Long (0x45)" (https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-54/out/en/host-controller-interface/host-controller-interface-functional-specification.html#UUID-927cb8c3-4a12-6154-d2f2-384f4a10f0a4)

[joey]

In the request_cb, I put only one piece of data into bt_le_per_adv_set_subevent_data each time, without combining multiple data entries. So 140 bytes per entry should be sufficient. When using the 2M rate, storing data this way works fine.

so,Does this mean the controller is using S=8 coding, and the encoded data length exceeds the specified limit?

[Vidar Berg]

The excerpt I posted in my previous reply states that this error is returned when the data length is greater than what can be transmitted in the current subevent interval. Yes S=8 coding is used.

[joey]

Can this limit be modified? I want to send longer data in synchronous broadcasting when using S=8 coding.

[Vidar Berg]

Did you try to extend the subevent interval?